The requirements for spermatozoa to acquire the ability to fertilize eggs and the mechanism of the acquisition of this ability will be studied in guinea pig and hamster spermatozoa. An in vitro capacitation and fertilization system in both guinea pig and hamster will be used to study the relationship of the type of metabolism to capacitation and fertilization. The occurrence of acrosome reaction will be the assay for completion of capacitation since both guinea pig and hamster spermatozoa have a very large, readily visible acrosome. Acrosome reaction studies will be used to explore a glucose effect on the acrosome reaction, the effect of an epididymal fluid component (EFC), and the effect of cAMP on capacitation. An inhibitory epididymal fluid component will be isolated and characterized. The levels of cAMP during capacitation will be determined as well as the interrelationship of these levels to glucose utilization.